The purpose of this project is to study pathogenesis and immunobiology of bacterial otitis media caused by nontypeable Haemophilus influenzae and Moraxella catarrhalis. In this fiscal year, efforts are focusing on developing an animal model for Moraxella catarrhalis since there is not a good animal model available for M. catarrhalis. Recently, a simple, reproducible, and non-invasive mouse pulmonary clearance model for M. catarrhalis via aerosol challenge was established. All of tested strains could be inoculated into mice at more than 100,000 colony-forming units (CFU)/lung. A maximum of 100 mice could be challenged per aerosol exposure. The number of bacteria inoculated in the lungs could be adjusted by the bacterial challenge concentration, the exposure time, and the negative pressure. This model will be useful for investigating the pathogenesis of M. catarrhalis, evaluating M. catarrhalis vaccine candidates and studying roles of immunity against M. catarrhalis. - Animal model, Aerosol Challenge, Moraxella catarrhalis, pulmonary clearance, otitis media